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Case studies

TWSS – Track Worker Safety Sites – Wickham Road, Retaining Structures

Geotechnical Design

Project Value: TBC

Project Commenced: December 2020

Project Completed: April 2021

Client: Network Rail

 

About the Project

EQUATE Design was awarded the contract to undertake designs proposing improvements to Track Worker Safety Sites. To provide scoping and design services to enable the upgrade of Network Rail authorised access points, to facilitate safe access for the workforce to undertake maintenance and upgrade works on the Network Rail infrastructure.  

The Wickham Road access point upgrade was one of the most challenging sites, where current access to the track was via a series of timber and concrete stairs built onto the side of the steep embankment. Most of the steps were in poor condition and therefore required replacing. 

The scope called for new stairs with new handrails on both sides of the stairs. 

 

The Challenge 

The existing stairs are non-compliant to both NR/CIV/SD/370 and BS5935-1. To provide compliant stairs an additional localised cut into the cutting slope is needed. In addition to meet the standard new stairway had to be split into three flight sections with intermediate landings. The top section had an additional constraint due to a Large London Plane tree, where the head of the stairs had to be aligned with the existing stair to avoid undermining the tree roots. Sections of the underbridge section had to be moved towards the embankment to meet the headroom clearance under the arch bridge. The main objective was to support the cutting, which could affect the stability of the embankment. 

 

The Solution 

Two solutions were considered during the design stage. The first was to regrade the cutting to create safe slope. This option was rejected due to the amount of regrading required and due to the fact that regrading would not prevent the top layers from flowing over. 

The second and preferred option was to install a ballast board retaining wall that would support the whole height of cutting. The wall was designed in accordance with IPS&E/EPF99/CIVILS/020. This solution proved economical and sufficient to retain cutting up to 900mm. 

 

The Deliverables: 

The works for pedestrian access sites mainly include the following elements of work: 

  • Topographical survey – prior to any design works, site is scoped and surveyed. 
  • Assessment of existing ground conditions – Earthwork Report is examined prior to the design stage. Ground conditions are verified to comply with the design requirements. 
  • Equate Design undertaking the design of the access stairs, ensuring compliance with the standards. 
  • The design is developed to provide access stairway to the track, ensuring the coordination with other elements like track layout and existing assets.  
  • The design focuses on providing compliant solution, stair, with intermediate landings providing safe point to stop if required. Significantly reducing the risk of falls. 
  • BCM Construction, the main contractor, coordinated the installation of the new flights of stairs, installation of yellow GRP handrailing and works to the existing boundary fencing and gates. 
  • In addition to the above items, retaining structures (ballast board retaining walls) have been installed to ensure resolve the embankment support and slope stability issues.

 

Outputs and Benefits:

Eliminated riskBy provision of the ballast board retaining wall, the risk of embankment failure was eliminated. By adopting this approach, BCM Construction & Equate Design were able to provide a safe and compliant access point solution with intermediate landings that provided a safe point to stop and rest if required.